The present invention relates to a device for lifting, gripping and transporting printing plates in a processing apparatus in which, during the processing in the individual stations, the printing plates are fixed by suction on a processing table. The device comprises a lifting device for the printing plates which is installed below the processing table and can be moved forward and backward in the longitudinal direction of the apparatus, and a gripping device which is installed above the processing table and can also be moved forward and backward in the longitudinal direction of the apparatus and by which the printing plates are taken up and transported onwardly.
The device described in U.S. Pat. No. 4,006,984 is especially suited for processing apparatuses wherein imaged printing plates, which can be directly used for printing, are prepared by electrostatically charging the printing plate, projecting the image of an original onto the printing plate, and subsequently developing, fixing and decoating the printing plate. These processing steps are carried out in the respective processing stations. In certain stations, e.g., in the exposure or developing station, the printing plate lies on a processing table which forms a chamber with a plurality of holes in its upper surface. Via a suction line, the chamber is linked with a vacuum pump. During the processing, the printing plate is firmly held in place on the processing table by the creation of a vacuum within the chamber. After completion of the respective processing step, air is introduced into the chamber, the printing plate is lifted, taken up by a gripping device and conveyed to the next processing station.
For lifting the printing plate, a lifting device installed below the processing station is used, wherein after the aeration, a pin is lifted by means of a driving means, and the plate is raised from the processing table by the pin. Before the next printing plate is transported onto the processing table, the pin is lowered again. However, the use of a special driving means, which must be controlled appropriately, makes this device very expensive and complicated. There is also the danger that, in case of a malfunctioning, the pin remains raised or cannot be lowered in time, and as a result the oncoming printing plate may be damaged.
The lifted plate is gripped and transported by means of a gripping device which can be moved forward and backward above the processing table in the longitudinal direction of the apparatus. A known gripping device has the shape of a clothespin. When this clothespin-type clamp is moved in the direction of the raised end of the printing plate, it is opened by a motor. As soon as the end of the printing plate rests in the opened clamp, the clamp is closed, and the device with the clamped-in printing plate is moved on to the next processing station. At the point where the printing plate is to be deposited again, the clamp opens. This gripping device requires complicated means for its adjustment. For opening the clamp, a driving means is needed which has to be appropriately controlled.